Lighting devices having light emitting diodes (“LEDs”) have typically required creating the LEDs on a semiconductor wafer using integrated circuit process steps. The resulting LEDs are substantially planar and comparatively large, on the order of two hundred or more microns across. Each such LED is a two terminal device, typically having two metallic terminals on the same side of the LED, to provide Ohmic contacts for p-type and n-type portions of the LED. The LED wafer is then divided into individual LEDs, typically through a mechanical process such as sawing. The individual LEDs are then placed in a reflective casing, and bonding wires are individually attached to each of the two metallic terminals of the LED. This process is time consuming, labor intensive and expensive, resulting in LED-based lighting devices which are generally too expensive for many consumer applications.
Similarly, energy generating devices such as photovoltaic panels have also typically required creating the photovoltaic diodes on a semiconductor wafer or other substrates using integrated circuit process steps. The resulting wafers or other substrates are then packaged and assembled to create the photovoltaic panels. This process is also time consuming, labor intensive and expensive, resulting in photovoltaic devices which are also too expensive for widespread use without being subsidized by third parties or without other governmental incentives.
Various technologies have been brought to bear in an attempt to create new types of diodes or other semiconductor devices for light emission or energy generation purposes. For example, it has been proposed that quantum dots, which are functionalized or capped with organic molecules to be miscible in an organic resin and solvent, may be printed to form graphics which then emit light when the graphics are pumped with a second light. Various approaches for device formation have also been undertaken using semiconductor nanoparticles, such as particles in the range of about 1.0 nm to about 100 nm (one-tenth of a micron). Another approach has utilized larger scale silicon powder, dispersed in a solvent-binder carrier, with the resulting colloidal suspension of silicon powder utilized to form an active layer in a printed transistor. Yet another different approach has used very flat AlInGaP LED structures, formed on a GaAs wafer, with each LED having a breakaway photoresist anchor to each of two neighboring LEDs on the wafer, and with each LED then picked and placed to form a resulting device.
Other approaches have used “lock and key” fluidic self-assembly, in which trapezoidal-shaped diodes have been placed in a solvent, and then poured over a substrate having matching, trapezoidal-shaped holes to catch and hold the trapezoidal-shaped diodes in place. The trapezoidal-shaped diodes in the solvent, however, are not suspended and dispersed within the solvent. The trapezoidal-shaped diodes instead settle out rapidly into clumps of diodes adhering to each other, are unable to be maintained in a suspension or otherwise dispersed within the solvent, and require active sonication or stirring immediately before use. Such trapezoidal-shaped diodes in a solvent cannot be utilized as a diode-based ink capable of being stored, packaged or otherwise used as an ink, and further are unsuitable for use in a printing process.
None of these approaches have utilized a liquid or gel containing two-terminal integrated circuits or other semiconductor devices which are actually dispersed and suspended in the liquid or gel medium, such as to form an ink, with the two-terminal integrated circuits suspended as particles, with the semiconductor devices being complete and capable of functioning, and which can be formed into an apparatus or system in a non-inert, atmospheric air environment, using a printing process.
These recent developments for diode-based technologies remain too complex and expensive for LED-based devices and photovoltaic devices to achieve commercial viability. As a consequence, a need remains for light emitting and/or photovoltaic apparatuses which are designed to be less expensive, in terms of incorporated components and in terms of ease of manufacture. A need also remains for methods to manufacture such light emitting or photovoltaic devices using less expensive and more robust processes, to thereby produce LED-based lighting devices and photovoltaic panels which may be available for widespread use and adoption by consumers and businesses. Various needs remain, therefore, for a liquid or gel suspension of completed, functioning diodes or other two-terminal integrated circuits which is capable of being printed to create LED-based devices and photovoltaic devices, for a method of printing to create such LED-based devices and photovoltaic devices, and for the resulting printed LED-based devices and photovoltaic devices.